Excessive aggression between weaned piglets after mixing is a welfare and production issue resulting in stress, injuries and economic losses. The aim of this study is to determine the effect of former acquaintance (FA) on aggression, lesion and growth performance in weaned, mixed piglets. The results showed that the FA group significantly reduced the number of fights, time spent fighting, number of bullying events, lesions, the average injury scores of the front site and middle site of weaned

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... glets after mixing. A significant interaction was found between the effects of sex and treatment on the number of fights won and bullying events, between the effects of days post-weaning and treatment on the lesion scores as well as between the effect of the lesion sites and treatments on the lesion score for all three days after mixing. The results suggested a potential welfare advantage to allow litters to have some acquaintance before weaning.